Elastomeric platform for furniture

ABSTRACT

1. A MEMBER ADAPTED FOR ATTACHMENT TO A FURNITURE FRAME COMPRISING AN ELSTOMERIC PLATFORM HAVING ADUROMETER, SHORE A, ASTM D-676-59T HARDNESS OF ABOUT 55 TO ABOUT 80, A MODULUS AT 50% ELONGATION, ASTM D412-62T FROM ABOUT 150 TO ABOUT 600 P.S.I., A TEAR RESISTANCE, ASTM D-624-54 DIE C OF AT LEAST ABOUT 100 POUNDS PER INCH AND A TENSION SET, ASTM D-412-62T OF NOT MORE THAN ABOUT 35% AND A PERMANENT SET NOT OVER ABOUT 15%.

1974 T. v. SAETHER 3,845,011

nmswouzmc rmvrroau pon mmnrruaa Original Filed Jan. 26, 1968 2 Sheets-Sheet 1 INVENTOR. ,TORE V. SAETHER ATTORNEYS Oct. 29, 1974 "r. v. SAETHER nmswomsmc PLATFORM FOR FURNITURE Original Filed Jab. 26,

FIG. 4

All? SUPPL Y INVENTOR." TORE v. SAETHER ATTORNEYS United States Patent U.S. Cl. 26042.32 1 Claim ABSTRACT OF THE DISCLOSURE An elastomeric platform for furniture is manufactured with particular control and correlation over four of its physical properties, so that the durometer, Shore A, hardness of the platform is from about 55 to about 80 (measured by ASTM D-676-59T); the modulus at 50% elongation of the platform is from about 150 to about 600 psi. (measured by. ASTM D412-62T); the tear resistance of the platform is at least about 100 pounds per inch (measured by ASTM D-624-54, die C); and the tension set of the platform is not more than about 35% (measured by ASTM D-412-62T). Such control and correlation achieve substantial improvements in the performance of the plat.- form when installed under tension as a supporting member in a furniture frame, these improvements including minimum permanent deflection and distortion of the platform by cold flow, minimum stress relaxation and consequent long life of the platform under severe conditions of use, and capability of the platform to be installed over a range of tensions from slightly above zero up to about 20% with full retention of the aforesaid advantages, whereby the platform is more versatile and useful as a supporting member in a greater variety of specific applications.

This application is a continuation-in-part of my copending application Ser. No. 710,418, Jan. 26, 1968, now Pat. No. 3,502,316 and of my earlier copending application Ser. No. 438,959, filed Mar. 11, 1965, now abandoned.

The present invention relates to an improved elastomeric platform which forms a support for cushions, upholstery and the like in articles of furniture. In some instances the platform may form the seating surface.

For many years strips of textile fabric have been widely used in articles of furniture as the support for cushions and the like. While such textile fabric strips provide a tion cost and extrusion of the upholstery down between I.

the strips.

More recently elastomeric platforms such as a rubber platform have been suggested as the support in place of the textile fabric strips. But in use these platforms have not proven to be entirely satisfactory. Up until now the elastomeric platform has been suspended in the furniture frame by means of metal clips or hooks. The metal clips are attached to the platform and special attachment means must be built into the frame of the furniture to accommodate the metal clips. The location of the attachment means in the frame must be indexed to correspond to the location of the metal clips carried by the platform. Building special attachment means into the furniture frame is expensive and it is virtually impossible to achieve such precise indexing that the platform in successive articles of 3,845,011 Patented Oct. 29, 1974 "ice furniture will have the desired resiliency when stretched to fit the frame. A description of such metal attachment clips may be found in patent application Ser. No. 265,932 filed Mar. 18, 1963.

Some improvement over the metal attachment clips can be realized at considerable expense by using adjustable turnbuckles in place of the clips. But adjustable turnbuckles do not solve the problem. As frequently happens it is necessary to adjust the span of the support to fit different articles of furniture by as much as three inches on each side. If this is done and the turnbuckles are fully extended, there is twelve inches of solid metal in the support which seriously impairs the comfort of the seat.

It also happens that each furniture manufacturer has his own specific requirements for the amount of resiliency and flexibility that is required in the base support. The required amount of resiliency and flexibility is determined by the particular article at hand and the characterstics of the cushions or upholstery padding. It has been determined that the resiliency and flexibility in a seat depend primarily upon the proper combination of stretch or ten sion in the platform, and also, the durometer hardness and modulus of the material from which the platform is made. In one article of furniture the desired seating comfortlmay be. achieved by stretching the platform up to 20% beyond normal dimensions and, in a different article of furniture, the same platform may be installed without stretch and just be drawn taut. Furthermore, within one article of furniture, the platform may be stretched as much as 20% in one direction and subjected to no stretch at all in another direction.

This practice of installing the elastomeric platform under widely different conditions of tension further complicates the problem. As is known, elastomers such as rubber when under tension for a period of time will take a permanent set and the amount of permanent set is, among other things,.a function of the state of cure and tension in the rubber. In use, as the elastomeric platform takes a permanent set, the comfort of the seat changes and a large amount of permanent set in the elastomeric platform will destroy seating comfort. In the case of metal attachment clips, this problem can be overcome by supplying different sized platforms tailor-made for a specified installation stretch, but this greatly increases the inventory which adds to the expense and handling problems.

The present invention overcomes these problems an there has been devised a satisfactory seating support which comprises an elastomeric platform havingphysical properties controlled within specified limits to maintain seating comfort over the range of tension customarily employed by furniture manufacturers, and to also achieve other substantial improvements in the performance of the platform. In a preferred embodiment resilient adjustable attachment means are employed for assembling the platform in a furniture frame.

When the physical properties of the platform are controlled and correlated to each other in accordance with the teachings of this invention, one important result is that the platform is subject only to a minimum of permanent deflection and distortion by cold flow and therefore the platform does not sag or otherwise gradually distort in a detrimental way over long periods of use. This important advantage of the platform is illustrated by the .fact that when heavy loads, e.g. 200 lbs., are continuously applied to it for long periods of up to 20 weeks,'the platform will deform permanently by cold fiow from its original configuration on the order of only up to 5% under the stated conditions.

. Another important advantage of an elastomeric platform made in accordance with the invention is that the platform undergoes only a minimum of stress relaxation after-it is subjected to regular pounding with a standard 3 weight for 250,000 to 500,000 cycles, which simulates up to years or more of actual use. Thus, the improved platform of the invention has a very long life and can be reliably used in applications involving years of use without the danger of failure.

A further advantage that is achieved in an elastomer platform made in accordane with the invention is that the platform can be installed in a furniture frame with a degree of stretch or tension anywhere within the range from slightly above zero (i.e., just taut) up to about without any appreciable impairment of the previouslydescribed advantages pertaining to the durability and long life of the platform. As a result, the platform is highly versatile and can be used to advantge in a greater variety of specific applications than can conventional platforms. This feature is not only important from the technical functional viewpoint but also from a commercial viewpoint because one of the problems that has been encountered heretofore with conventional elastomer platforms, due to inability to foretell the performance of any particular one of such platforms in any particular application, has been the relatively high costs and burdens of having to manufacture the platforms on a largely tailor-made basis geared to the mode of attachment, degree of installed tension, and other parameters of each specific application that have an effect upon the performance and life of the platform. Thus, the economic savings that would be derived from the ability to mass-produce a relatively small inventory of a few basic elastomer platforms, capable of being used in a wide variety of specific applications, has not been realized heretofore. With the high degree of versatility of elastomer platforms made in accordance with the invention, the aforesaid economic savings in manufacture are more readily achieved and this, in turn, should encourage more widespread use and acceptance of elastomer platforms.

As earlier mentioned, in order to achieve the advantages and benefits of the invention in an elastomer platform, control and correlation are necessary in particular man ner in four of the physical properties of the platform. Specifically, the platform must be manufactured to have a durometer, Shore A, hardness of from about 55 to about 80 measured by ASTM D-676-59T; a modulus at 50% elongation of from about 150 to about 600 p.s.i. measured by ASTM D-4l2-62T; a tear resistance of at least about 100 pounds per inch measured by ASTM D- 624-54, die C; and a tension set of not more than about 35% measured by ASTM D-4l2-62T. The aforesaid ASTM designations and those hereafter mentioned specifically refer to the corresponding test procedures thereby denoted, as prescribed by the American Society for Testing Materials for use as of Mar. 11, 1965.

Determination of the aforesaid physical properties which are critical and essential in the elastomeric platform was solved in research work by means of a simple testing device which simulated conditions of use in a furniture frame. First, the best combination of stretch, durometer hardness and modulus to get initial seating comfort was determined. Then, in the testing device, various platforms made with these different combinations were tested by repeatedly dropping a l40-pound weight in free fall on the elastomeric platform suspended with the resilient attachment means of the present invention. Using this device and the data obtained, it was then determined which physical properties not only gave initial seating comfort but also gave the maximum life before breaking and retained the seating comfort for the longest period of time. It was found that when the physical properties of the rubber were held within specific limits, an assembly could be obtained which would have optimum seating comfort over a long period of time and maximum life when subjected to repeated flexing.

The above-defined critical and essential physical properties in elastomer platforms made in accordance with the invention may be achieved by suitable selection of conventional elastomer and compounding ingredients and relative proportions thereof. As is well known in the art, the compounding of elastomer or rubber formulations can be varied in known ways to change the physical properties of an article that is cured and molded from the formulation, and the knowledge of a skilled person in the rubber compounding art is sufficient to enable him to decide which ingredient or which proportion of ingredient should be changed in order to bring about a desired change in the general direction or magnitude of any one of the final physical properties that are essential in the present invention.

Therefore, conventional elastomer ingredients, e.g. natural rubber, styrene-butadiene rubber, neoprene, butyl rubber, nitrile rubber, chlorosulfonated polyethylene elastomer, polystyrene elastomer, polybutadiene rubber, ethylene-propylene elastomers and ethylene-propylene-terpolymer elastomers, compounded with conventional ingredients such as carbon black and other inorganic solid fillers, curing agents, accelerators, promoters, lubricants, extenders, plasticizers, antioxidants and antiozonants, may be used to prepare formulations from which the improved platforms of the invention are produced by application of heat and pressure to the formulations in a platform mold, with suitable adjustments in the composition of the formulation by change of one or more ingredients therein and/ or of one or more relative proportions of ingredients therein as may be necessary to achieve the required critical and essential physical properties in the final platform.

The resilient attachment straps of the present invention are preferably made of textile fabric material such as the upholsterers tape customarily employed in conventional webbing sometimes used for forming the platform seat. The conventional upholsterers tape or strap comes in rolls and in order to mount the elastomeric platform in the furniture frame it is only necessary to slip the free end of the strap through an opening in the platform and then tack, staple or otherwise attach the free end of the strap to any desired portion of the furniture frame. Thereafter the strap is pulled tight to provide the desired installment stretch in the elastomeric platform and the second end of the strap is attached to the frame and cut off adjacent the place of attachment.

The resilient attachment straps of the present invention completely eliminate the need for building special attachment means into the frame of the furniture. The straps may be attached to the furniture frame in any desired location which is of advantage since the load can be distributed and correlated to the strength of the frame. The length of the straps can be readily adjusted to fit changes in dimension of the furniture frame and any desired installment stretch may be incorporated into the elastomeric platform in keeping with the required seating comfort for the padding which is to be used in the cushions or upholstery.

While the conventional upholsterers tape customarily used in furniture is preferred, the attachment straps may be made of any desired material provided however that the straps have some elastic resiliency but not more than one-half the elastic resiliency of the elastomeric platform. An elasticity in the strap which exceeds more than about one-half that of the elastomeric platform will interfere with control of the permanent set in the platform. Resilient elastic metal straps may be employed such as beryllium copper but as previously stated upholsterers tapes conventionally employed in furniture is preferred since the textile fabric is soft and its resiliency ideally fits the specified control of the permanent set of the platform.

Further details of the elastomeric platform of the present invention may be readily understood in connection with the description of the drawings which illustrate a preferred form of the invention and in which FIG. 1 is a top view illustrating the elastomeric platform in position in a wood furniture frame.

FIG. 2 illustrates use of a modified form of upholsterers tape. 1

FIG. 3 illustrates a preferred reinforcingof the openings in the platform.

FIG. 4 illustrates apparatus for determining the permanent set in the elastomeric platform.

FIG. 1 illustrates a top view of a wood frame such as may be used in a casualchair. The frame hasthe usual seat opening 12 and stretched across the opening is the elastomeric platform 14 with at'tachmentstraps'16 which in the preferred form of structure shown are upholsterer's tape of the type used in conventional articles of furniture; The elastomeric platform is 0.080 thick'and it is provided with a plurality of" openings 18- adapted to receive the straps. Best results in comfort'are achieved by'thinning the body'of the platform in the area between the open ings along the side of the platform (not shown). For example the thinned area may be 0.030 thick and extend from the edge of the body of the platform-inwardly to about or just beyond the inner edge of the openings and along the side tojust short of the side edge'of adjacent openings. Alternatively the rubber in the thinned area may be omitted so that the openings will be located in attach ment tabs as shown in the drawings of the-above 'mentioned'patent application Ser. No. 265,932. Abead of rubber (not shown) is preferably positioned along the periphery of the body portion of the platform" to increase resistance to tear. As illustrated at 16(a)' and 16(5) the elastomeric platform 14 is readily mounted across the opening of the frame by inserting the free end say -16(a) of a roll of upholsterers tape through the opening 18 and then'the free end is stapled, tacked or otherwise attached to the wood frame as at 20. The strap is then adjusted to the desired length and a second portion of the strap 16 (b) is attached to the wood frame as at 22. r

As shown in the preferred form of structure of FIG. 1 the strap in the chair forms a loop having two legs 16(a) and 16(b) each of which are spaced apart and attached to the wood frame at 20 and 22 respectively on either side of upright 24. It is not necessary to separate the legs of the loop of. the fabric strap and the legs may beattached to .the wood frame with one on top of the other as illustrated at 26. During assembly the length of the loop of each successive strap is adjusted to establish the particular tension or installation stretch desired bythe manufacturer.

As illustrated in the drawing the loop of the strap may vary inlength and the legs of the loop may'be attached in any desired location such as to avoid an upright 24 or to distribute the load in the frame as illustrated at 28 where the two legs of the loop have a tendency to pull the adjacent sides of the frame together. Any convenient arrangement of the loops is possible and the points of attachment of the legs of the loop may be selected independently of the location of the openings 18. Change in dimension of the wood frame is readily compensated for by changing the length of the loop without change in tension or streach of the platform and without any noticeable change in seating comfort.

While the looped strap of FIG. 1 is the preferred form of structure, a single strap with only one leg may be used as illustrated in FIG. 2. As there shown a metal rod or other convenient keeper 30 is sewed or otherwise attached in a loop of the strap 31 as at 32 and in such case the strap is cut to a predetermined length of about three to six inches. The keeper is made large enough so that it will not pass through the opening 18. In use the free end 34 of the strap is pulled through the opening 18 and then attached to the wood frame with adjusted length for the tension or stretch desired in the platform.

The elastomeric platform shown in FIG. 1 is generally a square but it will be understood that the platform may be of any desired configuration such as that which is for example shown in a copending patent application Ser. No. 265,932 filed Mar. 18, 1963.

r.s-The:.openings 18 of the platform are preferably reinforced for added strength by means of an insert such as the metal rod36 which is embedded in the rubber so that the. middle; portion of the rod will reinforce the outside edge of the hole as shown in FIG. 3. A metal plate (not shown) with opening corresponding to opening 18 may also be embedded in the rubber to strengthen the opening The elastomeric platform 14 shown in FIG. 1 is made of cured rubber and any of the known synthetic plastic elastomersmay be employed. But in order to avoid excessive sagging and to preserve the desired resiliency and flexibility for seating comfort under the varied conditions of installation tension which ranges from just pulling the platform up taut to stretching it up to twenty or more percent of its normal dimension, the elastomeric platform must be made from a material having certain physical properties. The determination of the life of the elastomeric platform and from this the determination of the optimum physical properties is arrived at readily by means of the apparatus illustrated in FIG. 4.

In carrying out the test the distance across the central area of the body of the platform 14 in a direction parallel to the side is measured between the inner edge of each of two opposite openings 18 with the platform at room temperature. As illustrated in FIG. 4, the platform 14 is then suspended over the opening 38 in a wood frame 39 by means of resilient attachment straps 16. The straps are so fastened to frame 39 that the platform when suspended over the opening is stretched to about 10% greater dimensions 'than'its normal dimensions. This simulates the mean of the tension to which the platform is subjected when suspended in the frame of furniture. The frame 39 is positioned on a support plate 40 with platform 14 located over the opening 42 in the support plate. Conventional keepers 44 hold the wood frame in position on plate Plate 40 is mounted in a frame 45. A weight 46 of one hundred and forty pounds having a bottom surface in the form of a cylinder six inches in diameter is suspended above the platform 14 by means of a conventional air lift 48. The air lift is adapted to lift the weight 46 up until it is four inches above the plane of the platform whereupon the weight drops by free fall onto the platform. A conventional cyclic timer 50 controls the dropping rate to twelve -cycles or blows per minute. The platform is subjected to five hundredblows after which it is removed from the wood frame and allowed to relax for thirty minutes. The distance across the central area of the body of the platform in a direction parallel to the sides is again measured between the inner edge of each of the same two opposite openings 18 with the platform at room temperature. The permanent set is determined by the following formula:

Distance after pounding-Original distance Original distance X =Percent permanent se't From this testing it has been determined that in order to get a platform with a satisfactory life and acceptable minimum sag materials with the following physical properties are necessary as determined by the prescribed ASTM procedures.

The compounding of rubber and other elastomers to the above specifications is well known in the art. In general the thickness of the platform is from about 0.015 to about 0.150 but depending upon the article of furniture at hand other thicknesses may be employed.

In research work it was found that a platform with the above stated physical characteristics did not rupture under the test for permanent set andrthe percentage of permanent set did not exceed fifteen percent. With a permanent set of not more than fifteen percent the seating 10 comfort was satisfactory for the range of installment tension conventionally employed. Preferably the percent of permanent set is not more than five percent for best results.

As a specific embodiment of the invention, the following elastomer formulation was prepared from the indicated ingredients and proportions thereof expressed in parts by weight:

*This extender had a viscosity (Saybolt Furol) at 140 F. of 250 to 350 seconds.

'lhis wax had a viscosity (ASTM D-446) at 210 F. of 45 SUS maximum, a melting point (ASTM D-87) of 150 F. minimum, a specific gravity at 60 F. of 0.928 and an oil con tent (ASTM D-721) of 0.5 maximum.

The foregoing formulation was cured under heat and pressure in a platform mold and the resulting platform had the following physical properties:

8 Physical property: Value Shore A durometer hardness (ASTM D676-59T) 465 lbs./in. Modules at elongation (ASTM D'- 41262T) 70. Tear resistance (ASTM D62454, die

C) 245 psi. Tension set (ASTM D-4l2-62T) 20%.

Accordingly, the final platform had the essential controlled and correlated physical properties and was capable of providing the previously-described advantages and benefits of the invention.

As used in the description the term furniture includes all the usual household furniture such as beds, chairs, sofas, day beds and the like as well as the usual furniture in trains, busses, airplanes, ships and the like. The frame of the furniture need not be wood and may be made of metal or the plastic materials conventionally employed.

It will be understood that it is intended to cover all changes and modifications of the preferred form of invention herein chosen for the purpose of illustration which changes and modifications do not constitute a departure from the spirit and scope of the invention.

What is claimed is:

1. A member adapted for attachment to a furniture frame comprising an elastomeric platform having a durometer, Shore A, ASTM D67659T hardness of about to about 80, a modulus at 50% elongation, ASTM D' 41262T from about 150 to about 600 p.s.i., a tear resistance, ASTM D-624-54 die C of at least about pounds per inch and a tension set, ASTM D-4l2-62T of not more than about 35% and a permanent set not over about 15%.

References Cited UNITED STATES PATENTS LEWIS T. JACOBS, Primary Examiner 11.8. C1. X.R.

260763, 42.33, 42.33, 42.34, 42.35, 42.36; 297Dig. 2

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 5$ Dated 061591991" lgyh f. E tier Inventor(s) T vae 1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 8, Lines 1 et al: Phvsical Propertv should read Physical Property Value Shore A durometer hardness (ASTM D-676-59T) 70 Modulus at 507 elongation (ASTM D-4l2-62T) 245 p.s.i. Tear resistance (ASTM D-624-54, die C) 465 lbsa/in. Tension set (ASTM D-4l2-62T) 2070 Col. 1, Lines 4 and 37: "Continuation-in-part of application Serial Noa 710,418" should read-' Division of application Serial No. 710,418-- Signed and sealed this 17th day of June 1975.

(SEAL) Attesc: w

1 C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks =ORM PC3-1050 (10-69; USCOMM-DC 60376-P69 U45 GUVERNMEN! PRINTING OFFICE: 93 o 

1. A MEMBER ADAPTED FOR ATTACHMENT TO A FURNITURE FRAME COMPRISING AN ELSTOMERIC PLATFORM HAVING ADUROMETER, SHORE A, ASTM D-676-59T HARDNESS OF ABOUT 55 TO ABOUT 80, A MODULUS AT 50% ELONGATION, ASTM D412-62T FROM ABOUT 150 TO ABOUT 600 P.S.I., A TEAR RESISTANCE, ASTM D-624-54 DIE C OF AT LEAST ABOUT 100 POUNDS PER INCH AND A TENSION SET, ASTM D-412-62T OF NOT MORE THAN ABOUT 35% AND A PERMANENT SET NOT OVER ABOUT 15%. 